[Info-vax] Dvorak on Itanic

[JF Mezei]

Christopher wrote:
>
> IA-64 processors are completely capable of explicit multi-threading.

But isn't this decision done by the compiler at compile time ?

The Alpha presentations I had mentioned that while IA64 compilers can do
a good job of optimizing code to run fast on IA64, they cannot predict
the flow of the code because the compilers don't know what data will be
processed.

By having brains in the CPU at run time (as opposed to brains in the
compiler), real world applications will run much faster.

But if you have a fixed task (like calculating PI to 50 billion
decimals), then IA64 will fare well because the code will execute in the
precise way that the compiler predicted.


What I find interesting is that from Intel's point of view, the original
intent of IA64 was to replace the 8086, and as such, a "general" CPU
would have been what was needed, not a CPU whose philosophy was suited
more for high performance calculations rather than general computing.

Note that Alpha also had some serious mistakes early on with the
engineers having omitted fast access to unaligned bytes (such as wen
processing strings of characters). But those were implementation
problems, not architecture/philosophy problems.